You can reduce the CPU and RAM resources below the above-specified minimum for development and testing purposes.
The specification can be as low as 1GB of free RAM beyond operating system requirements and a single CPU core.
However, you must use at least the required minimum specification for production.

Recommended Specifications

Four core 64-bit x86 CPU running at 3GHz; six cores when using Cross Datacenter Replication (XDCR) and Views.

16GB RAM (physical).

A local block-based storage device (hard disk, SSD).
Network filesystems such as CIFS and NFS are not supported.

These recommended specifications do not take into account your intended workload.
You should follow the sizing guidelines detailed in Sizing Guidelines when deciding on machine specifications to run Couchbase Server.